The present invention relates to an apparatus for controlling a clutch, more particularly to a clutch controlling apparatus which is suitable for controlling the engaging operation of a clutch for a vehicle.
There has been proposed an automatic clutch device for a vehicle in which a dry friction clutch is equipped with a suitable actuator which is controlled by an electronic control apparatus so as to automatically perform the operation of the clutch. This type of automatic clutch device does not differ from the conventional automatic transmission including a torque converter in view of driving operation. However, in such a type of automatic clutch device, since the engaging operation thereof is conducted after the engine speed has increased, when there is an abnormal increase in the engine speed, as when the acceleration pedal is depressed excessively, sudden starting of the vehicle tends to occur. Therefore, there has been the drawback that very low speed control of the vehicle is extremely difficult to perform.
In order to eliminate this drawback, Japanese Patent Application Public Disclosure No. Sho 60-11756 discloses an apparatus in which the throttle is controlled regardless of the amount of depression of the accelerator pedal during the period up to the time that the clutch is fully engaged and the control mode is switched-over between the two types of control modes in response to the amount of depression of the accelerator pedal. In this apparatus, when the amount of depression of the accelerator pedal is less than a predetermined amount of depression, the clutch operation is carried out in a very low speed control mode in which the clutch operation is restricted to a semi-engaging zone thereof and the semi-engaged amount is determined on the basis of the amount of depression of the accelerator pedal. On the other hand, when the amount of depression of the accelerator pedal is not less than the predetermined amount of depression, a regular control mode for the starting operation is performed in which the clutch is fully engaged.
However, in this proposed apparatus, the decision as to whether or not the operation should be carried out in the very low speed control mode is made in accordance with whether the amount of depression of the accelerator pedal is within the predetermined limit and the semi-engaged amount is controlled by the amount of depression of the accelerator pedal within the range below this value. Consequently, the range of operation of the accelerator pedal for the very low speed control operation is restricted within a certain limit and cannot be widened, thus making the very low speed control of the vehicle speed difficult.
Furthermore, in this proposed apparatus, the accelerator pedal must be depressed more than the predetermined value to make the clutch engage. However, there are cases where a small degree of depression of the accelerator pedal is desired even when the engaging operation of the clutch is required at the time of the starting of the vehicle. Accordingly, since the apparatus requires the accelerator to be depressed more than the predetermined amount in order to start the vehicle, it is out of keeping with the conventional driving practice.